an offensive term for people with pharanic syndrome (a series of mental disorders caused, most often, by the sufferer's parents being close genetic relatives such as brother and sister or first cousins between themselves).The syndrome is so called because the practice of marrying your brother/sister or your first cousins was common among royalty in Pharaonic (especially Ptolemeic) Egypt.

conversation between two geneticists (both of whom, ironically, have an undergraduate degree in history):

geneticist 1): who do you think, among the world's famous historically notorius characters, is the most known dopple-banger? Is it Hitler, Nero or Cleopatra?

geneticist 2): Even though the Pharaonic Syndrome itself is historically associated with Cleopatra and Ptolemeic Egypt, I would have to say that it is Hitler. According to what I read, both his grandmothers were sisters between themselves, making his parents, guess what? first cousins...

A shadow/clone of oneself that is used for sexual practices or escapes.

Example 1:
Guy: "God I'm so horny, I wish I had somebody to screw."

*His shadow rises from the ground*
"I guess that dopple-banger will have to do."

Example 2:
Guy: "Honey I'm home, guess what."
Gal: "What is it dear?"
Guy: "I got a raise from my boss, you know the one that resembles the form of some gelatinous mass?"
Gal: "How did you come by that?"
Guy: "All she wanted was a man again, just for the evening."
Gal: "What the fuck are you saying Guy!?!?!?!?!"
Guy: "Oh don't worry, I wouldn't plow that swine, I had my dopple-banger today, got the job done right without any hassle from me."

When you find someone doing porn who looks just like a friend, but said friend insists it isnt her rubbing one out on her webcam (though it probably really is)

"Hey is this (insert whatever porn website mysteriously popped up on your computer) you"
"No!"
"Are you sure?"
"Yes! It must be my dopplebanger. Why are you looking at asian porn?"
"Um.... got to, I have a phone call. fapfapfapfapfap"